Sparking plug



Dec. 1, 1931. HUFISCHER 1,834,608

sgiARKINe PLUG Filed May 28. 1928 Patented Dec. 1, 1931 UNITED STATES PATENT OFFICE HERMANN FISCHER, F BERLIN-NEUKOLLN, GERMANY, ASSIGNOR, BY MESNE ASSIGN- MENTS, TO PAUL REINHARDT, OF BERLIN, GERMANY SPARKING PLUG Application filed May 28, 1928, Serial No. 281,239, and in Germany June 4, 1927.

My invention relates to sparking plugs and it is an object of my invention to provide a plug in which the good insulating and other properties of certain materials are fully 5 utilized and the influence of their less desirable properties is elin'iinatcd.

To this end, I provide resilient supporting means for supporting such insulating materials.

0 Failure of sparking plugs is a frequent cause of trouble in the operation of internal combustion engines, and of grave accidents, as in airplanes. The excellent properties of quartz glass as an insulating material are 5 fully appreciated and it has often been attempted to equip sparking plugs with quartz insulators, but heretofore such insulators were liotsatisfactory on account of their short life.

0 This drawback is overcome in my invention in which a quartz tube surroimding the inner electrode of the sparking plug is provided so as to be absolutely tight under maximum compression and explosion pressures, 5 but is supported by resilient means.

I shall describe a sparking plug having an insulating tube of quartz glass, but it is understood that I am not limited to this material as not only quartz glass but quartz and all other suitable materials, as ceramic materials, may be used. Preferably the softening temperature of the material is beyond the average temperature in the combustion chamber of the cylinder.

In the accompanying drawing I have illustrated an axial section of a sparking plug according to my invention, on an enlarged scale.

Referring now to the drawing, a is the silicate inserted between the flange g and the inner end of. the electrode insulating tube 03, L are washers of silicate on the outer end of the tube (Z, Z is a washer of aluminium or the like placed on the washers 7a, m is a ring of resilient material, and n is a nut on a threaded portion 00f the electrode 0 which exerts thrust on the ring on and holds the tube 03 under the resilient pressure of the ring. m.

p are washers of mica or other silicate which are placed over the tube (Z in a cavity of the sleeve 6 and are bored tapering so as to fit the taper of the tube (l, g is a threaded sleeve in the cavity of the sleeve 1), 1' is a shoulder at the end of the cavity on which the set of washers p are supported, 8 is a tube of insulating material which is seated on the sleeve g, and t is a nut on the thread of the electrode which exerts thrust on the tube 8.

The plug is assembled as follows:

The silicate rings h are placed on the flange g, thesheath (Z is wound tightly about the inner electrode 0, the tube (1 is placed on the washers h with its end i which is ground exactly square, the washers 7: are placed on the outer end of the tube (Z, the aluminium washer l is placed on the washers la, the ring m is inserted between the washer l and the nut a, and the nut is set. The assembled inner electrode unit is then inserted in the is inserted, the tube 8 is placed on the sleeve 9 and the nut is set.

The annular clearance 0 between the electrode c and the tube (1 is important as it prevents short-eircuiting of the electrode 0 past the mica washers b to the body of the plug when the tube d should become cracked, and

carbon particles should penetrate into the clearance e. A further protection is afforded by the sheath f. Gas or a, vacuum may be present in the clearance e.

The washers h and 7c constitute resilient cushions which, together with the ring m, absorb the thrust of the nut 12, and prevent damage to the tube (1. Besides, they form tight packings. The washers p serve the same objects, forming a sort of resilient bearing for the tube d. Resilient support of the tube (Z is, as mentioned, particularly important when the tube is of quartz or quartz glass.

The tube .9 is a protecting casing and may be of quartz, ceramic material, silicates, as mica, and the like, and resilient, if desired. Preferably, the material of the tube 03 and of the washers p which surround the tube,

should have equal, or substantially equal, ex-

pansion coelficients, a condition which is 111- filled in the case of quartz and mica.

I claim:

1. A sparking plug comprising a body forming an outer electrode, an inner electrode arranged within the body, an inner insulating tube arranged in spaced surrounding relation about the inner electrode and having a conical outer surface, an outer insulating tube having a conical inner surface, means on the body for forcibly inserting the .outer insulating tube into the body. and

means on the inner electrode to draw firmly the inner insulating tube into the outer insulating tube.

2. A sparking plug comprising a body forming an outer electrode, an inner electrode arranged within the body, an inner insulating tube arranged in spaced surrounding relation about the inner electrode and having a conical outer surface, anouter insulating tube having a conical inner surface and composed of rings of mica, means on the body for forcibly inserting the outer insulating tube into the bod and between the body and the inner insulating tube and means on the inner electrode to draw firmly the inner insulating tube into the outer insulating tube.

3. A sparking plug comprising a sectional body forming an outer electrode, an inner electrode arranged within the body, an inner insulating tube arranged in spaced surrounding relation about the inner electrode, an outer insulating tube surrounding the inner insulating tube, means for forcibly inserting the outer insulating tube into the body, a collar on'the inner end of the inner electrode, a layer of mica wrapped about the inner electrode adjacent the fiafnge, mica layers on said collar for supporting the inner insulating tube, clamping means adjustably mounted on the outer end of the inner electrode, and a resilient ring, an aluminium washer and mica layers successively interposed between the clampingmeans and the outer end of the inner insulating tube.

In testimony whereof I aflix my signature.

HERMANN FISCHER. 

